It is often necessary to use a pressure transducer to measure the pressure of a media that must be tightly contained. Often in the case of such media, even a very small leak in the header of the transducer can be highly dangerous. This problem is illustrated in FIG. 1 which shows a conventional pressure transducer including a pressure sensor 1 mounted to a standard header assembly 2. The header assembly 2 is coupled to a port element 7, which in turn, may be coupled to a pressure source. The port element 7 and the header assembly 2 are coupled to a transducer body element 3. Behind the header assembly 2 there is a large cavity 4 that houses the electronics. A typical leak path of the media, denoted by numeral 5, enters at the junction of the port element 7 and the housing 6 of the header assembly 2, and extends into the cavity 4.
Pressure transducers, such as illustrated in FIG. 1, currently used for measuring such media, are commonly leak checked before installation in the field. These leak checks involve pressurizing the transducer with a gas, such as helium, and measuring the rate at which the helium leaks past the header assembly 2 into the cavity 4.
There are two problems with this leak checking method. The first problem is that the test must be done in a special test fixture and can not easily be performed when the pressure transducer is installed for normal use. This means that any leak that develops after installation will go unnoticed until a new periodic leak check is done. The second problem is that even highly accurate leak checkers have a finite resolution below which a leak can not be detected. For most applications this resolution is more than adequate for safety needs. However, there are some applications involving highly volatile or poisonous gases, where even a miniscule leak is unacceptable.
Thus, highly accurate leak detection, which can be performed while a pressure transducer is installed in the field, is needed.